Cap job for Fender 5e5-A with Astron Caps?

[Robert Technology]

Hello!

I'm working on a 50's Fender 5e5-a that's all original with Astron caps throughout. The guy wants me to get it into reliable condition for some shows, and the technician in me is saying to pull all the electrolytics, despite the fact that they are all vintage Astron caps. It currently holds stable B+ voltages and sounds KILLER as is...

I know that those caps are on borrowed time at this point, but I basically am looking for some validation from those of you with more experience that I'm not doing this guy a disservice by replacing every electrolytic capacitor.

[xtian]

It's tough to make these decisions for other people! But I'm hearing he wants reliability for public gigs, and that means new caps. The amp isn't a museum exhibit--it has to perform at volume, regularly. Unsolder the originals and pack them away. The only advantage to having the original electrolytic in there is "collectable" sale value of the amp, and if he's not planning to sell it, change 'em.

My clients sometimes ask, "will it change the tone?" The answer is, "YES. It will make the tone better."

[DRH1958]

Yep agree. For reliability, I would replace them. You don't want it to fail at a gig. I would be tempted to up the uF rating on those first two to 30uF. Definitely keep the signal caps though.

[The Dude]

I don't disagree at all with the above. I have a slightly different approach on these sorts of things. I like to just lay it out with the customer and let them decide. Explain both scenarios (to cap or not to cap). Sometimes it comes down to money and sometimes reliability, but I like to give customers the option up front. Most customers will appreciate your honesty and, either way, you're off the hook. If they decide not to replace caps and one fails, it was their decision. If they decide to replace the caps, they know up front what the repair cost will be so they don't whine about the bill.

[Tom Phillips]

If the parts are original the amp will also have the yellow Astron non-electrolytic tubular caps installed. My experience is that they do not hold up like the blue tubular caps in the later Fenders. They usually fail a DC leakage test. This is another thing to discuss with your customer. I'm not recommending shotgun replacement but they should be checked.

[Mick Bailey]

You could have an old 50s car with the original oil filter, plugs, points and fluids. As much as you'd want it to stay that way, time is your enemy and can't be beaten. So if you wanted to drive that car an maintain its reliability, those things have to be replaced. Whilst it breaks my heart to even disturb those original solder joints in a vintage amp, the reality is they were just a consumer product and not designed to last anywhere near as long as they have done.

Where customers want to keep both the internal appearance and modern reliability there are a number of techniques you can use;

1. In some cases good reproductions are available, or ones that look period. I've seen good replicas of Astron caps, but there are some other branded caps that look pretty good.

2. New electrolytics can be stripped of their heatshrink, new labels printed up on an inkjet or laser printer and then use clear heatshrink tubing over the top. Quick and easy. At least it looks superficially better than using out-of-the-box parts. You can even print out a replacement sleeve on thick paper and stick it to a thin card backing and use this to re-wrap a new cap, Then seal it with clear lacquer or potting wax. You can get a good vintage look by printing onto paper cut from a stout brown envelope.

3. Sometimes old components can be hollowed out and a modern (smaller) component fitted in the internal space and sealed back up. Cardboard sleeved caps can be unrolled at one end and the can slipped out. The cardboard tube can rehouse a new cap, though some ingenuity may be required to get the ends looking correct unless a new cap can be found that's a good fit.

4. I've seen some replica caps where a modern component has had a resin shell cast around it in a 2-part split mould to replicate the original. You can make a mould off the original component using silicone and talcum powder.

[Justin Thomas]

Okay, often paralyzed by being able to see both sides of the issue... If the amp is going out on the road, far from the TLC you would show this amp, do everything in your power to make it as reliable as possible. But if is for local gigs with easy access to you, I'd say check thoroughly as it is, and don't change anything that's not conclusively in imminent danger of destructive failure. Given that it sounds great and seems to be working fine, I have no reason to think it'll crash overnight.

If the amp has been played regularly at the same settings of "gig-volume" for quite some time, I'd leave it as is, <IF> it was staying close enough to home to fix in a day's time. So I would do this based on my ability to execute a speedy repair, the distance it was travelling, and how reliable it's been for the last few months IF it's been well-used and otherwise thoroughly tested and is plugging along just fine. Along with that, do you have the parts on-hand to replace anything that may fail in the amp?

Also - he does carry a spare amp, right? Given the unreliability and inevitable failure of that dino-tech tube amp, right? >:O

I know my opinion will probably differ from others, but I also have a much more open schedule to do speedy repairs than most... So I'm not arguing with any of the above...

Justin

Edit: re: #3 above, yes, it' s VERY easy to cram a modern cap inside the paper casing of an old paper-wrapped lytic. Maybe a bit m ore time-consuming, but keeps the look. Just make sure Tue next time the amp is serviced, some indiscriminate tech doesn't toss all those old original-looking caps!

[Robert Technology]

Thanks for the information everyone! I apologize for my first post here being a request for opinions about vintage capacitors!

I'm still waiting on parts, but am going to plan on replacing the filter caps, bias cap, and plate resistors. All other caps will be checked for leakage before replacing, but anything that is showing signs of trouble will probably be taken out.

The amp belongs to a band-mate of mine, and he's owned it since he was a kid. It's really beat up cosmetically, and will be gigged regularly, but only around town. He's really just hoping to get it as reliable as possible while still maintaining "that sound." Not a cork-sniffer by any means -- I'm sure he wouldn't even flinch if I pulled every capacitor, but I'd rather maintain as much of the originality as possible for him if the parts still check out as being within tolerance.

Thanks again, and I'll post pics when it's done if there is any interest.

[ThermionicScott]

I don't know that I'd automatically replace all of the plate resistors -- if any are excessively noisy, sure, but even if some have drifted, that might be part of the "killer" sound you hear.

[Randall]

I always tell customers, "In MY Opinion", electrolytics that are past their bedtime should be replaced. It will not hurt the sound, quite the opposite. The internet has created this issue of everything must be kept original for the best sound, which is BS. I have never heard an argument for keeping old electrolytics in a vintage amp that I believe.

[Jazz P Bass]

Personally, I would be leery of the statement that new ECaps "will not hurt the sound".

It's a can-o -worms.

Yes, new caps will be less likely to fail.

But, the old caps, while drifting south, may just be the ticket for that 'brown sound'.

[Robert Technology]

I really appreciate all of the input you guys have given! Can't believe it took me so long to come across this forum.

It seems like the general consensus is that the Filter caps and the Bias cap should be changed in almost all cases. I know that talking vintage caps is a can-o-worms (to quote Mr. Jazz P Bass), but in an attempt to approach this in a logical way I've compiled the following list.

I've left the things that I am less sure about in bold, and any input is greatly appreciated! Here is my understanding of what can happen when other parts are changed, or left alone until catastrophic failure, in a vintage amp like this:

Coupling caps:
-Can potentially increase or decrease the quality of tone when changed (depending on experience/opinion).
-If originals are left in place can leak DC to following stages which can cause red-plating of tubes or further damage to downstream components that are not meant to see that DC voltage.

Bypass caps:
-Can potentially increase or decrease the quality of tone when changed (depending on experience/opinion).
-Since these are at a lower voltage than filter caps seem to be less likely to catastrophically fail, unless cap is visually bulging, or leaky.
-Most of these caps are arranged such that the negative side is tied to ground, thus any DC leakage will simply go to ground rather than being passed onto a further stage and causing damage.

Plate resistors:
-Can potentially increase or decrease the quality of tone when changed (depending on experience/opinion).
-Can cause that "swirling" sound if left unchecked and have drifted too far out of tolerance.
-Catastrophic failure hinders ability to play the amp, but is very unlikely to damage other components.